Military term for a unit or group of soldiers sent away from the main force for a specific purpose.
A detachment was dispatched to the front line.
He led a small contingent on a reconnaissance mission.
派遣隊 also means a dispatched unit, but 分遣隊 emphasizes the splitting off from a main body, often with a more temporary or specialized mission.
Compound of 分 (ぶん, 'divide, part') + 遣 (けん, 'dispatch') + 隊 (たい, 'squad, unit'). The term follows standard Sino-Japanese word formation for military units.